This invention relates generally to flat panel display devices and particularly to an electron beam clean up structure for such devices.
U.S. Pat. No. 4,069,439 discloses a flat panel display device including a pair of spaced parallel beam guide meshes between which electrons are propagated as beams. Arranged between the guide meshes at the end where electrons enter the guide structure are two additional meshes which narrow the electron propagation space for an initial portion of the beam guide structure. These additional meshes are used to capture electrons which are propagating near the guide meshes and thereby serve as beam clean up meshes. Operationally, the use of such clean up meshes is satisfactory. However, the additional meshes add complexity and cost to the display device and create a problem in aligning the clean up members with the guide meshes.
U.S. Pat. No. 4,128,784 also shows a flat panel display device utilizing parallel spaced electron beam guide meshes between which electrons are propagated as beams. The ends of the beam guides nearest th cathode are bent to converge toward one another and thereby narrow the space between which electrons can be injected into the propagation space. The bent portions, therefore, serve as a beam clean up means. This device is not adequate for high performance beam clean up because only a small number of electrons are captured by the bent portions. The major portion of the electrons have a velocity vector directed such that they miss the bent portions and enter the narrow space between the guide meshes and propagate along the beam guide near the guide meshes.